Advances in the field of semiconductor integrated circuits (ICs) have brought about higher levels of integration. Accordingly, semiconductor manufacturing process advancements are driving the corresponding geometric dimensions of semiconductor devices to decreasingly smaller values. 10 micrometer (μm) gate lengths, for example, were common in the 1970's, but continuously advancing semiconductor manufacturing processes have reduced gate lengths to well below 100 nanometers (nm) for deep sub-micron integrated circuit (IC) design.
One key challenge presented by deep sub-micron design is the adjustment of the various semiconductor processing steps that are required to implement devices within a silicon die so as to obtain acceptable yield and manufacturability. While such process adjustments may optimize operating parameters at a particular process corner, the process adjustments may nevertheless produce degraded operating parameters at other process corners.
Operating parameters, such as transistor threshold voltage, leakage current, and saturation current, for example, may be so affected by the process variations that performance of the devices no longer corresponds to design specifications previously verified within the design/simulation environment. As a result, process variations that optimize yield and manufacturability may also contribute to detrimental effects on device performance, such as increased leakage current, reduced threshold voltage, and/or increased saturation current.
As geometric features of the deep sub-micron devices continue to shrink, scaling, implant, and annealing process variations invoke increasingly significant device performance degradations. Reducing the effects of such process-based performance variations have conventionally been implemented either by specifically designing the semiconductor processing steps to minimize process-induced performance degradation, or by changing the equipment used during one or more of the semiconductor processing steps.
Voltage and temperature variation, however, may also lead to variations that degrade performance of the semiconductor device over all process, voltage, and temperature (PVT) corners. As a result, a device that exhibits acceptable performance levels at a first PVT corner, may nevertheless exhibit performance degradations at other PVT corners that are dynamically induced.
Efforts continue, therefore, to devise alternate solutions to mitigate the effects of PVT variation on device performance.